Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing
Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing
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DOI：
10.1038/s41598-020-58598-z
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发表时间：
2020-02
影响因子：
4.6
通讯作者：
V. Thampy;A. Fong;N. Calta;Jenny Wang;Aiden A. Martin;P. J. DePond;Andrew M. Kiss;G. Guss;Q. Xing;R. Ott;Anthony W. van Buuren;M. Toney;J. Weker;M. Kramer;M. Matthews;Christopher J. Tassone;K. Stone
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文献类型：
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作者：
V. Thampy;A. Fong;N. Calta;Jenny Wang;Aiden A. Martin;P. J. DePond;Andrew M. Kiss;G. Guss;Q. Xing;R. Ott;Anthony W. van Buuren;M. Toney;J. Weker;M. Kramer;M. Matthews;Christopher J. Tassone;K. Stone
激光粉末床熔融（LPBF）是一种增材制造方法，其特点是高功率激光在薄金属粉末床上快速扫描以形成单层，然后可以在其上构建形成更大的结构。与传统的冶金工艺相比，许多熔融、再凝固和随后的冷却以更高的速率和更高的热梯度进行，其中大部分发生在地表以下。我们利用高速x射线衍射法提取了Ti-6Al-4V钛合金熔体再凝固后β- transsus上方的亚表面冷却速率。我们观察到激光功率与体冷却速率成反比关系。测量的冷却速率与少数β- ti相所承受的残余应变水平相关，在较慢的冷却速率下应变增加。α- ti相表现为晶格收缩，且随冷却速率不变。我们还观察到，在较慢的冷却速率下，β- ti相的衍射峰展宽更大，LPBF后相对相分数发生了变化。这些结果提供了地下热历史的直接测量，并证明了它对增材制造材料的最终质量的重要性。
Laser powder bed fusion (LPBF) is a method of additive manufacturing characterized by the rapid scanning of a high powered laser over a thin bed of metallic powder to create a single layer, which may then be built upon to form larger structures. Much of the melting, resolidification, and subsequent cooling take place at much higher rates and with much higher thermal gradients than in traditional metallurgical processes, with much of this occurring below the surface. We have usedin situhigh speed X-ray diffraction to extract subsurface cooling rates following resolidification from the melt and above theβ-transus in titanium alloy Ti-6Al-4V. We observe an inverse relationship with laser power and bulk cooling rates. The measured cooling rates are seen to correlate to the level of residual strain borne by the minorityβ-Ti phase with increased strain at slower cooling rates. Theα-Ti phase shows a lattice contraction which is invariant with cooling rate. We also observe a broadening of the diffraction peaks which is greater for theβ-Ti phase at slower cooling rates and a change in the relative phase fraction following LPBF. These results provide a direct measure of the subsurface thermal history and demonstrate its importance to the ultimate quality of additively manufactured materials.